Method and device for electroplating fastener chain

TECHNICAL FIELD

The present invention relates to a method for electroplating a fastener chain having metal element rows. The present invention also relates to an electroplating device suitable for the electroplating method.

BACKGROUND ART

Some slide fasteners include element rows made of a metal, and such slide fasteners are generally referred to as "metal fasteners". The metal fasteners are generally produced via an intermediate product called a fastener chain which is formed by engaging metal element rows fixed to opposing side edges of a pair of elongated fastener tapes. The fastener chain is cut at a predetermined length, and various parts such as a slider, upper stoppers, a lower stopper and the like are attached to complete the metal fastener.

The metal fasteners often use copper alloys or aluminum alloys, and are suitable for designs that take advantage of color and texture of metals. Recently, there are various needs of user for the design of the metal fastener, and various color tones are required depending on applications. One of methods for changing the color tone of a metal product is electroplating. In the electroplating method, an object to be plated is immersed in a plating solution and energization is conducted to form a plating film on a surface of the object to be plated.

Most electroplating methods for metal fasteners use barrel plating in which an object to be plated is placed in a barrel, the barrel is introduced into a plating solution, and electroplating is carried out while rotating the barrel (e.g., <patcit id="pcit0001" dnum="JP20041000011A"><text>Japanese Patent Application Publication No. 2004-1000011 A</text></patcit>, <patcit id="pcit0002" dnum="JP2008202086A"><text>Japanese Patent Application Publication No. 2008-202086 A</text></patcit>, <patcit id="pcit0003" dnum="JP3087554B"><text>Japanese Patent No. 3087554 B</text></patcit>, and <patcit id="pcit0004" dnum="JP5063733B"><text>Japanese Patent No. 5063733 B</text></patcit>).

Further, as an electroplating method for an elongated product, a method is known in which electroplating is carried out while continuously conveying the elongated product in a plating bath (e.g., <patcit id="pcit0005" dnum="JP2004076092A"><text>Japanese Patent Application Publication No.2004-76092A</text></patcit>, <patcit id="pcit0006" dnum="JPH05239699A"><text>Japanese Patent Application Publication No. H05-239699 A</text></patcit>, and <patcit id="pcit0007" dnum="JPH08209383A"><text>Japanese Patent Application Publication No. H08-209383 A</text></patcit>).

However, the above methods do not consider specificities of the metal fasteners. In the metal fastener, adjacent elements are not electrically connected to each other, so that it is difficult to electroplate uniformly each element by the above method. Therefore, to plate the metal fastener, a method is proposed in which a fastener chain is produced in a state where elements have been electrically connected in advance, and the fastener chain is continuously subjected to electroplating. For example, <patcit id="pcit0008" dnum="JP2514760B"><text>Japanese Patent No. 2514760 B</text></patcit> proposes to produce a fastener chain in a state where elements are electrically connected, by knitting conductive yarns into an element attachment portion of a fastener tape.

However, although the method as described in <patcit id="pcit0009" dnum="JP2514760B"><text>Japanese Patent No. 2514760 B</text></patcit> can simultaneously carry a current to the entire element row to electroplate it continuously, it has a problem that the conductive yarn is expensive, and the conductive yarn is easily cut and the metal is easily dissolved in preparation and dying of the tape due to knitting of the metal conductive yarn, so that productivity is poor.

As a technique for electroplating elements of a slide fastener chain without using the conductive yarn, a feeding drum method is known. For example, <patcit id="pcit0010" dnum="JPH083158A"><text>Japanese Examined Patent Application Publication No.H08-3158 A</text></patcit> discloses a method for surface-treating both front and back sides of an element by axially supporting a pair of feeding drums each having a predetermined structure in parallel, and providing a positive electrode on one side of a feeding drum A and providing a positive electrode on the other side of another feeding drum B so as to be opposite to each other, and connecting a negative electrode to feeding shafts of the feeding drums A and B, in which a slide fastener chain C having metal elements is first pressed on and passed through the one side of the feeding drum A and is then pressed on and passed through the other side of the feeding drum B.

Further, <patcit id="pcit0011" dnum="CN102839405B"><text>Chinese Patent No. 102839405 B</text></patcit> discloses an electroplating device for elements of a fastener chain, comprising: an arc-shaped guide rail for housing and guiding a fastener tape, wherein a conductive portion of an outer periphery of the guide rail connected to a power supply is brought into contact with bottom portions of the elements during housing of the fastener tape.

<patcit id="pcit0012" dnum="CN105755515A"><text>Chinese Patent Application No. 105755515 A</text></patcit> discloses a device for electroplating a fastener chain comprising a plating bath and a conductive cover constituting the anode and forming a container when placed in abutment with the bottom surface of the plating bath, said container being configured to enable the fastener chain to pass therethrough. The fastener chain is cathodically biased by sliding contact with a cathode.

Patent Literatures

<ul id="ul0001" list-style="none" compact="compact"><li>Patent Document 1: <patcit id="pcit0013" dnum="JP2004100011A"><text>Japanese Patent Application Publication No. 2004-100011 A</text></patcit></li><li>Patent Document 2: <patcit id="pcit0014" dnum="JP2008202086A"><text>Japanese Patent Application Publication No. 2008-202086 A</text></patcit></li><li>Patent Document 3: <patcit id="pcit0015" dnum="JP3087554B"><text>Japanese Patent No. 3087554 B</text></patcit></li><li>Patent Document 4: Patent No. <patcit id="pcit0016" dnum="JP5063733B"><text>5063733 B</text></patcit></li><li>Patent Document 5: <patcit id="pcit0017" dnum="JP2004076092A"><text>Japanese Patent Application Publication No. 2004-76092 A</text></patcit></li><li>Patent Document 6: <patcit id="pcit0018" dnum="JPH05239699A"><text>Japanese Patent Application Publication No. H05-239699 A</text></patcit></li><li>Patent Document 7: <patcit id="pcit0019" dnum="JPH08209383A"><text>Japanese Patent Application Publication No. H08-209383 A</text></patcit></li><li>Patent Document 8: <patcit id="pcit0020" dnum="JP2514760B"><text>Japanese Patent No. 2514760 B</text></patcit></li><li>Patent Document 9: <patcit id="pcit0021" dnum="JPH083158B"><text>Japanese Examined Patent Application Publication No. H08-3158 B</text></patcit></li><li>Patent Document 10: <patcit id="pcit0022" dnum="CN102839405B"><text>Chinese Patent No. 102839405 B</text></patcit></li><li>Patent Document 11: <patcit id="pcit0023" dnum="CN105755515"><text>Chinese Patent Application No. 105755515</text></patcit></li></ul>

SUMMARY OF INVENTION

Technical Problem

The feeding drum method tends to result in non-uniform contact of the feeding drum with the elements, so that it is necessary to prepare a large number of feeding drums and repeat contacting in order to eliminate elements on which a plating film has not been formed. This leads to necessity of a large-scale and expensive plating device.

Further, a large number of repetitions of contacting with the feeding drum causes a problem of resulting in large variation in thickness of the plating film. The large variation in thickness of the plating film results in appearance appearing to be uniform color tone, but quality such as corrosion resistance, abrasion resistance and discoloration resistance depending on types of plating varies for each element, resulting in deterioration starting from an element with a thinner plating film. Further, a large difference of the thickness of the plating film does not provide any fixed sliding resistance in operation of a slider, causing the user to feel discomfort. Therefore, the metal fastener having the large variation in thickness of the plating film on the element cannot be a high-quality metal fastener.

Furthermore, the barrel plating has a risk that a large number of elements will mesh with one another during rotation of the elements in the barrel. If they mesh with one another until the end of the plating process, they can be removed as defects. However, if the meshing is released in the middle of the process, the film thickness of the meshed part will be decreased. Therefore, it is difficult to form a highly uniform plating film as designed. Moreover, in the barrel plating, the plating film is formed on the entire surface of the element, so that plating is also formed on a surface portion of the element that is not visible after being implanted in the fastener tape, which will waste the plating solution. Further, the implanting of the elements in the fastener tape before being plated tends to result in deformation of the elements and generation of cracks in a step of caulking the elements. The cracks lead to poor appearance and also tend to generate discoloration originated from the cracks.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide an electroplating method that can conveniently form a plating film having improved uniformity and adhesiveness on the exposed surface of individual elements of a metal fastener even if the elements are not electrically connected to each other in advance. Another object of the present invention is to provide an electroplating device suitable to carry out such an electroplating method.

Solution to Problem

The present inventor has conducted intensive studies in order to solve the above problems, and found that it is effective to bring each metal element fixed to a fastener chain into contact with a plurality of conductive media flowably accommodated and apply a current via the conductive media while traveling the fastener chain in a plating solution. Then, the present inventor has found that, by ensuring the contacting of the metal elements with the plating solution while disposing the conductive media on a first main surface side of the fastener chain without disposing the conductive media on the second main surface side when the metal elements are brought into contact with the conductive media, a plating film is grown with high uniformity on a surface of the element on the second main surface side. That is, the present inventor has found that a current can be reliably carried to the individual elements by plating the metal element on one side across the fastener tape at one time.

In this method, basically no plating film grows on the surface of the element exposed on the first main surface side during forming the electroplating film on the surface of the element exposed on the second main surface side. However, depending on a composition of the plating solution and a material of the metal element, displacement plating may occur on the surface of the element exposed on the first main surface side. That is, when plating is performed on one side at one time, the element exposed on the first main surface side has a stand-by time from the start of contacting with the plating solution to electroplating, so that the displacement plating may occur during that stand-by time. The displacement plating which is a type of electroless plating results in lower adhesion than that of electroplating. Therefore, when the displacement plating occurs on the surface of the element exposed on the first main surface side, the adhesiveness of the resulting plating film will be deteriorated even if the electroplating film is formed on the surface of the element exposed on the first main surface side after the displacement plating occurs. Thus, it is desirable not to generate the displacement plating on the surface of the element exposed on the first main surface side during electroplating of the surface of the element exposed on the second main surface side of the fastener chain.

The present inventor has studied a method for preventing the displacement plating, and as a result, the present inventor has found that it is effective to complete first electroplating on the surface of the element exposed on the second main surface side as soon as possible, and to start first electroplating on the surface of the element exposed on the first main surface side. Once a thin electroplating film is formed on the element surface, the problem of displacement plating is eliminated. Thus, after that, there is no need to worry about the time for electroplating on each side. The stand-by time from the start of contacting of the element surface on one side with the plating solution to the start of the first electroplating on that surface is important.

Advantageous Effects of Invention

According to the present invention, even if the fastener chain is not in a state where the elements are electrically connected to each other in advance, the individual elements will be reliably subjected to power supply while bringing the individual elements into sufficient contact with the plating solution when electroplating the fastener chain, so that a highly uniform plating film can be formed in a short period of time. Further, according to the present invention, the displacement plating is suppressed, so that a plating film having high adhesiveness can be obtained. In other words, the method for electroplating the metal fastener according the present invention can also be versatile for the purpose of rapidly forming a thin plating film on the surface of the element regardless of the composition of the plating solution and the material of the metal elements. The present invention can also be used as a strike plating method before main plating on the elements of the metal fastener.

Further, according to the present invention, the size of the plating device can be decreased, so that installation costs and maintenance costs can be reduced. The conductive media may also be plated, but the conductive media are flowably accommodated and can be separately removed from the plating device, which also provides an advantage of easy maintenance of the device. Therefore, the present invention can be an innovative invention that will contribute to enabling proposal of inexpensive fastener products having a wide variety of color tones to users.

BRIEF DESCRIPTION OF DRAWINGS

<ul id="ul0002" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a schematic front view of a metal fastener.</li><li><figref idref="f0002">FIG. 2</figref> is a partial schematic view when one (or other) main surface of a fastener chain is observed from a direction perpendicular to the main surface.</li><li><figref idref="f0003">FIG. 3</figref> is a schematic cross-sectional view of an insulating container as viewed from a direction facing a conveying direction of a fastener chain when the fastener chain moves straight to pass through the insulating container of a plating device according to the present invention.</li><li><figref idref="f0004">FIG. 4</figref> is a schematic cross-sectional view taken along the line A-A' of the insulating container shown in <figref idref="f0003">FIG. 3</figref>.</li><li><figref idref="f0005">FIG. 5</figref> is a schematic cross-sectional view taken along the line B-B' when conductive media and a fastener chain are removed from the insulating container shown in <figref idref="f0003">FIG. 3</figref>.</li><li><figref idref="f0006">FIG. 6</figref> shows a first overall structural example of an electroplating device according to the present invention.</li><li><figref idref="f0007">FIG. 7</figref> shows a second overall structural example of an electroplating device according to the present invention.</li><li><figref idref="f0008">FIG. 8</figref> shows a schematic plan view (upper side) and a schematic side view (lower side) of a third overall structural example of an electroplating device according to the present invention.</li><li><figref idref="f0009">FIG. 9</figref> shows a schematic plan view (upper side) and a schematic side view (lower side) of a fourth overall structural example of an electroplating device according to the present invention.</li><li><figref idref="f0010">FIG. 10</figref> shows a schematic plan view (upper side) and a schematic side view (lower side) of a fifth overall structural example of an electroplating device according to the present invention.</li><li><figref idref="f0011">FIG. 11</figref> shows a sixth overall structural example of an electroplating device according to the present invention.</li><li><figref idref="f0012">FIG. 12</figref> shows an overall structure of an electroplating device according to Comparative Example 1.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1. Metal Fastener)

<figref idref="f0001">FIG. 1</figref> exemplarily shows a schematic front view of a metal fastener. As shown in <figref idref="f0001">FIG. 1</figref>, the metal fastener includes: a pair of fastener tapes 1 each having a core portion 2 formed on an inner edge side; rows of metal elements 3 caulked and fixed to the core portions 2 of the fastener tapes 1 at predetermined spaces; upper stoppers 4 and a lower stopper 5 caulked and fixed to the core portions 2 of the fastener tapes 1 at upper ends and lower ends of the rows of the metal elements, respectively; and a slider 6 disposed between the rows of the pair of opposing elements 3 and slidable in an up and down direction for engaging and disengaging the pair of metal elements 3. An article in which the row of the elements 3 has been fixed to one side edge of one fastener tape 1 is referred to as a fastener stringer, and an article in which the rows of opposing elements 3 of a pair of fastener stringers have been engaged with each other is referred to as a fastener chain. It should be noted that the lower stopper 5 may be an openable, closable and fittingly insertable tool consisting of an insert pin, a box pin and a box body, so that the pair of slide fastener chains can be separated by engaging and disengaging operations of the slider. Other embodiments that are not shown are also possible.

<figref idref="f0002">FIG. 2</figref> shows a partial schematic view when one (or the other) main surface of the fastener chain is observed from a direction perpendicular to the main surface. Each metal element 3 is provided with a pair of leg portions 10 for pinching the fastener tape 1 from both main surface sides, and a head portion 9 for connecting the pair of leg portions 10 and for engagement. Here, a boundary between the leg portion 10 and the head portion 9 is a straight line extending in a longitudinal direction of the fastener tape 1, which passes through an inner peripheral portion closest to the head portion among the portions where the fastener tape 1 can enter between both leg portions 10 (see the dotted line C in <figref idref="f0002">FIG. 2</figref>).

In the present invention, when a first (or a second) main surface of the fastener chain is observed from the direction perpendicular to the main surface, an intersection portion Q of a straight line bisecting the element 3 in the longitudinal direction of the fastener tape 1 (the direction A in <figref idref="f0002">FIG. 2</figref>) and a straight line bisecting the element 3 in a direction perpendicular to the longitudinal direction (the direction B in <figref idref="f0002">FIG. 2</figref>) is referred to as an element center on the first (or the second) main surface side of the fastener tape 1 (see <figref idref="f0002">FIG. 2</figref>).

Materials of the metal elements 3 that can be used include, but not particularly limited to, copper (pure copper), copper alloys (red brass, brass, nickel white, and the like) and aluminum alloys (Al-Cu alloys, Al-Mn alloys, Al-Si alloys, Al-Mg alloys, Al-Mg-Si alloys, Al-Zn-Mg alloys, Al-Zn-Mg-Cu alloys and the like), zinc, zinc alloys, iron, iron alloys, and the like.

The metal elements can be subjected to various electroplating. The plating can be performed aiming at a rust prevention effect, a crack prevention effect, and a sliding resistance reduction effect, in addition to the design purpose of obtaining a desired color tone. A type of plating is not particularly limited and may be any of single metal plating, alloy plating and composite plating. Examples of the plating includes Sn plating, Cu-Sn alloy plating, Cu-Sn-Zn alloy plating, Sn-Co alloy plating, noble metal plating (e.g., Au plating, Ru plating, Rh plating, Pd plating). Further examples of the plating includes Zn plating (including a zincate treatment), Cu plating (including copper cyanide plating, copper pyrophosphate plating, and copper sulfate plating), Cu-Zn alloy plating (including brass plating), Ni plating, Ru plating, Au Plating, Co plating, Cr plating (including a chromate treatment), Cr-Mo alloy plating and the like. The type of plating is not limited to those, and other various metal plating can be performed in accordance with the purpose.

According to the present invention, the displacement plating is suppressed, thereby allowing a uniform and highly adhesive plating film to be formed regardless of components of a plating solution and materials of the metal elements. Therefore, it is possible to provide metal fasteners having various color tones by freely combining the materials of the metal elements and the materials of the plating.

The slide fastener can be attached to various articles, and particularly functions as an opening/closing tool. The articles to which the slide fastener is attached include, but not limited to, daily necessities such as clothes, bags, shoes and miscellaneous goods, as well as industrial goods such as water storage tanks, fishing nets and space suites.

(2. Plating Method)

In one aspect, the invention proposes a method for continuously electroplating the fastener chain having the rows of the metal elements while conveying the fastener chain.

In one embodiment, the electroplating method according to the present invention includes: <ol id="ol0001" compact="compact" ol-style=""><li>A) a first electroplating step including causing the fastener chain to pass through one or more first insulating container(s) while bringing each metal element into contact with a plating solution in a plating bath, the first insulating container(s) flowably accommodating a plurality of conductive media in electrical contact with a negative electrode, for the purpose of mainly plating the surface of the metal element row exposed on one main surface side of the fastener chain; and</li><li>B) a second electroplating step including, after the first electroplating step, causing the fastener chain to pass through one or more second insulating container(s) while bringing each metal element into contact with a plating solution in a plating bath, the second insulating container(s) flowably accommodating a plurality of conductive media in electrical contact with a negative electrode, for the purpose of mainly plating the surface of the metal element row exposed on the other main surface side of the fastener chain.</li></ol>

By carrying out these two steps, it is possible to plate the surface of the metal element rows exposed on both main surface sides of the fastener chain. Moreover, by carrying out both of the steps using different plating solutions, it is also possible to form a plating film on one main surface of the fastener chain that is different from that on the other main surface.

In one embodiment of the fastener stringer according to the present invention, the rows of the metal elements are fixed to the fastener tapes and then plated, so that a plating film is not formed on a portion of the surface of each metal element which is hidden by contact with the fastener tape. This will lead to saving of the plating solution and contribute to reduction of production costs.

Conditions such as a composition and a temperature of the plating solution and the like may be appropriately set by those skilled in the art depending on types of metal components to be deposited on each element, and are not particularly limited. Zinc is an amphoteric metal which is easily dissolved in acid and alkali, and also has a higher ionization tendency, so that it easily generates substitution reaction with other metals. Therefore, in particular when the metal element containing zinc is subjected to plating, the adhesiveness of the plating film tends to be reduced. When the metal element containing zinc is subjected to copper plating, the displacement plating is difficult to occur if a copper cyanide plating solution is used, but in metal fasteners it is desirable to use a non-cyan copper plating solution in terms of safety. However, there is a problem that the use of the non-cyan copper plating solution easily leads to the displacement plating. According to the present invention, the displacement plating can be suppressed even if the non-cyan copper plating solution which will otherwise lead to the displacement plating is used.

Materials of the conductive media are not particularly limited, and are generally metals. Among the metals, iron, stainless steel, copper and brass are preferable, and iron is more preferable, because they have higher corrosion resistance and higher abrasion resistance. However, when using conductive media made of iron, the contact of the conductive media with the plating solution will lead to formation of a displacement-plating film having poor adhesion on surfaces of iron balls. The plating film peels off from the conductive media during electroplating of the fastener chain to form fine metal pieces which float in the plating solution. The floating of the metal pieces in the plating solution leads to adhesion to the fastener tapes, and it is thus preferable to prevent the floating. Therefore, when using the conductive media made of iron, it is preferable that the conductive media have been previously subjected to copper pyrophosphate plating, copper sulfate plating, nickel plating or tin-nickel alloy plating in order to prevent the displacement plating. Although the displacement plating can also be prevented by copper cyanide plating on the conductive media, it leads to relatively large irregularities on the surfaces of the conductive media so that rotation of the conductive media is inhibited. Therefore, copper pyrophosphate plating, copper sulfate plating, nickel plating, or tin-nickel alloy plating is preferred.

Materials of the first insulating container(s) and the second insulating container(s) include, preferably, high density polyethylene (HDPE), heat resistant hard polyvinyl chloride, and polyacetal (POM), and more preferably high density polyethylene (HDPE), in terms of chemical resistance, abrasion resistance, and heat resistance.

A plurality of conductive media flowably accommodated in the first insulating container(s) and in the second insulating container(s) are in electrical contact with the negative electrode, so that power can be supplied from the negative electrode to each element via the conductive media. The negative electrode may be disposed at a non-limiting position, but it is desirable to dispose the negative electrode at a position where the electrical contact with each conductive medium is not interrupted in each insulating container.

For example, when using a fixed cell type electroplating device as described below, the fastener chain passing through the first insulating container(s) and the second insulating container(s) in the horizontal direction leads to movement of the conductive media to the front side in the conveying direction and to accumulation there. The fastener chain passing through the first insulating container(s) and the second insulating container(s) vertically upward leads to tendency of the conductive media accumulated downward.

Therefore, when the fastener chain passes in the horizontal direction, the negative electrode is preferably disposed at least on the front inner side in the conveying direction where the conductive media are easily accumulated, among the inner sides of the insulating container(s). When the fastener chain passes vertically upward, the negative electrode is preferably disposed at least on the lower inner side of the insulating container where the conductive media are easily accumulated, among the inner sides of the insulating container(s). The shape of the negative electrode is not particularly limited, and it may be, for example, a plate shape.

The fastener chain can also travel in an oblique direction in the middle of the horizontal direction and the vertical direction. In this case, the position where the conductive media are easily accumulated varies depending on the inclination, traveling speed, number and size of the conductive media. Therefore, the position where the positive electrode is disposed may be adjusted according to the actual conditions.

The conductive media are flowable in each insulating container, and as the fastener chain travels, the conductive media constantly changes the contact position with each element while being flowed and/or rotated and/or moved up and down. This can allow growth of a plating film having high uniformity because the position of current passing and the contact resistance are also changed constantly. The shape of each conductive medium is not limited as long as the conductive media are contained in the container(s) in a flowable state, but preferably it is spherical in terms of flowability.

An optimum diameter of each conductive medium varies depending on a chain width of the fastener chain, as well as a width and pitch of the slider sliding direction of the elements. When using a fixed cell type electroplating device as described below, the diameter of each conducive medium is preferably equal to or more than the chain thickness in order to prevent the conductive media from entering the traveling path of the fastener chain and the traveling path from being clogged by the conductive media while the fastener chain passes through the first insulating container(s) and the second insulating container(s). Further, in terms of efficient growth of a plating film having high uniformity by bringing the fastener chain into contact with a large number of conductive media at a short passing distance while the fastener chain passes through the first insulating container(s) and the second insulating container(s), the diameter of each conductive medium is preferably 3 times or less, and more preferably 2.5 times or less, and still more preferably 2 times or less as large as the chain thickness. Here, the diameter of each conductive medium is defined as a diameter of a true sphere having the same volume as that of the conductive medium to be measured.

The number of conductive media to be accommodated in the first insulating container(s) and the second insulating container(s) is not particularly limited, and is preferably set as needed in view of being able to supply power to each element of the fastener chain, in particular of ensuring a sufficient quantity of the conductive media to maintain a constant contact with each element during passing through the first insulating container(s) and the second insulating container(s) even if the conductive media move in the traveling direction. On the other hand, it is preferable that an appropriate pressing pressure is applied from the conductive media to each element of the fastener chain because it allows facilitation of flow of electricity, but an excessive pressing pressure increases conveying resistance to hinder smooth conveying of the fastener chain. Therefore, it is preferable that the fastener chain can smoothly pass through the first insulating container(s) and the second insulating container(s) without experiencing the excessive conveying resistance. From the above point of view, illustratively, the quantity of the conductive media accommodated in each insulating container is preferably such that 3 or more layers (in other words, a lamination thickness of 3 or more times as large as the diameter of the conductive medium), and typically from 3 to 8 layers (in other words, a lamination thickness of from 3 to 8 times as large as the diameter of the conductive medium) can be formed when the conductive media spread over the elements.

When using a fixed cell type electroplating device as described below, the horizontal passing of the fastener chain through the first insulating container(s) and the second insulating container(s) moves the conductive media to the front in the conveying direction to facilitate accumulation. Thus, the weight of the conductive media accumulated in the front presses the fastener chain, and the conveying resistance to the fastener chain increases. Further, when current flows from the negative electrode to the conductive media, a longer length of a cell drops voltage, thereby decreasing a plating efficiency. Therefore, the connecting of two or more of each of the first insulating container(s) and the second insulating container(s) in series can allow a decrease in conveying resistance due to the weight of the conductive media, and can allow an increased plating efficiency. It is also possible to adjust the thickness of the plating film and the traveling speed of the fastener chain by increasing or decreasing the number of two or more of insulating containers connected in series.

In terms of reducing the conveying resistance, it is desirable to provide an upward angle in the traveling direction of the fastener chain passing through each insulating container, that is, the fastener chain passing through each insulating container while rising. Thus, the conductive media which are easy to move in the conveying direction falls to the rear in the conveying direction due to its own weight, so that the conductive media are not likely to accumulate at the front of the conveying direction. The inclination angle may be appropriately set according to the conveying speed, the size and number of conductive media, and the like. When the conductive media are spherical and the quantity of the conductive media are such that from 3 to 8 layers can be formed over the elements, the inclination angle is preferably 9° or more, and typically 9° or more and 45° or less, in terms of maintaining the contact of the conductive media with the elements passing through the first insulating container(s) and the second insulating container(s) even if the conductive media move in the traveling direction during traveling of the fastener chain.

In terms of designing a more compact plating device, there is also a method in which the fastener chain passes through each insulating container while rising in the vertical direction. According to the method, the plating bath is elongated in the vertical direction and shortened in the horizontal direction, so that a footprint for disposing the plating device can be reduced.

In the first electroplating step, during the fastener chain passing through the first insulating container(s), power is supplied by mainly bringing the surface of each metal element exposed on the first main surface side of the fastener chain into contact with the conductive media in the first insulating container(s). During the step, the first positive electrode is disposed in a positional relationship so as to face the surface of each metal element exposed on the second main surface side of the fastener chain, so that regular flows of cations and electrons are generated, and a plating film can be rapidly grown on the surface of each metal element exposed on the second main surface side of the fastener chain. In terms of suppressing the plating of the conductive media, the first positive electrode should be preferably disposed only in the positional relationship so as to face the surface of each metal element exposed on the second main surface side of the fastener chain.

In the second electroplating step, during the fastener chain passing through the second insulating container(s), power is supplied by mainly bringing the surface of each metal element exposed on the second main surface side of the fastener chain into contact with the conductive media in the second insulating container(s). During the step, the second positive electrode is disposed at a positional relationship so as to face the surface of each metal element exposed on the first main surface side of the fastener chain, so that regular flows of cations and electrons are generated, and a plating film can be rapidly grown on the surface of each metal element exposed on the first main surface side of the fastener chain. In terms of suppressing the plating on excessive areas other than the elements, the second positive electrode should be preferably disposed only in the positional relationship so as to face the surface of each metal element exposed on the first main surface side of the fastener chain.

When a plurality of conductive media is randomly brought into contact with both of the main surfaces of the fastener chain, the plating film grows on the conductive media, but no plating film grows on the element surface. Therefore, it is preferable that the surface exposed on one main surface side is preferentially contacted with the conductive media as much as possible. Therefore, during the fastener chain passing through the first insulating container(s), 60% or more, and preferably 80% or more, and more preferably 90% or more, and even more preferably all of the total number of conductive media in the first insulating container(s) are configured to be contactable with the surface of each metal element exposed on the first main surface side of the fastener chain. The expression "all of the conductive media in the first insulating container(s) are configured to be contactable with the surface of each metal element exposed on the first main surface side of the fastener chain" means that only the surface of the metal elements exposed on the first main surface side is brought into contact with the conductive media in the first insulating container(s).

Similarly, during the fastener chain passing through the second insulating container(s), 60% or more, and preferably 80% or more, and more preferably 90% or more, and even more preferably all of the total number of conductive media in the second insulating container(s) are configured to be contactable with the surface of each metal element exposed on the second main surface side of the fastener chain. The expression "all of the conductive media in the second insulating container(s) are configured to be contactable with the surface of each metal element exposed on the second main surface side of the fastener chain" means that only the surface of the metal elements exposed on the second main surface side is brought into contact with the conductive media in the second insulating container(s).

In the first electroplating step, the plating film basically does not grow on the element exposed on the first main surface side. However, since the elements exposed on the first main surface side are placed under conditions that can be in contact with the plating solution, the displacement plating may occur. As described above, the plating film formed by the displacement plating has weaker adhesiveness than the film formed by electroplating. Therefore, it is desirable to suppress the displacement plating as much as possible. If the displacement plating occurs on the surface of the element exposed on the first main surface side, then the adhesion of the plating film is lowered even if electroplating is subsequently performed on the surface of the element exposed on the first main surface side. Therefore, in the first electroplating step, it is desirable not to cause the displacement plating on the surface of the element exposed on the first main surface side.

To prevent effectively the displacement plating on the surface of the element exposed on the first main surface side, it is important to start power supply to the surface of each metal element exposed on the second main surface side of the fastener chain in the second electroplating step within 30 seconds, preferably within 20 seconds, more preferably 10 seconds, even more preferably within 10 seconds after the surface of each metal element exposed on the first main surface side in the first electroplating step is initially contacted with the plating solution.

However, if the timing of the start of power supply to the surface of each metal element exposed on the second main surface side of the fastener chain in the second electroplating step is too fast, the plating film does not sufficiently grow on the surface of each exposed metal element on the second main surface side in the first electroplating step. Therefore, the power supply to the surface of each metal element exposed on the second main surface side of the fastener chain in the second electroplating step is preferably started in 5 seconds or more, more preferably 7 seconds or more, even more preferably 9 seconds or more, after the surface of each metal element exposed on the first main surface side is initially contacted with the plating solution in the first electroplating step, depending on conditions such as compositions and current densities of the plating solution.

In the first electroplating step, a plating film having a thickness of 0.1 µm or more is preferably formed at the element center Q of each metal element exposed on the second main surface side, in terms of exerting a desired function on the plating film. The thickness of the plating film is more preferably 0.15 µm or more, and still more preferably 0.2 µm or more. An upper limit of the thickness of the plating film is not particularly limited, but according to the above restriction of within 30 seconds or less, the upper limit is about 20 µm, typically 0.5 µm or less, even if the practical range of the applied voltage is taken into consideration.

Similarly, in the second electroplating step, the plating film having a thickness of 0.1 µm or more is preferably formed at the element center Q of each metal element exposed on the first main surface side. The thickness of the plating film is more preferably 0.15 µm or more, and still more preferably 0.2 µm or more. An upper limit of the thickness of the plating film is not particularly limited, but in terms of forming the plating film having an equivalent thickness on the surface of the metal element exposed on both of the main surface sides of the fastener chain, the thickness of the plating film at the element center Q exposed on the second main surface side in each metal element is preferably from 0.7 T to 1.3 T, and more preferably from 0.8 T to 1.2 T, and still more preferably from 0.9 T to 1.1 T, in which T represents the thickness of the plating film at the element center Q exposed on the first main surface side.

Thickness of the plating film at the element center Q of each element is determined by obtaining an element depth profile with Auger electron spectroscopy (AES). The thickness of the plating film is defined to be a depth at which a concentration of the plating metal element is half of the maximum value. Analysis conditions are as follows: <ul id="ul0003" list-style="none" compact="compact"><li>Acceleration Voltage: 10kV;</li><li>Amount of Current: 3 x 10^-8 A;</li><li>Ion Gun: 2kV;</li><li>Measuring Diameter: 50 µm;</li><li>Etching: Measured every 20 seconds; and</li><li>Sample Inclination: 30°.</li></ul> A detection depth is calculated using an etching rate of 8.0 nm/in of the SiO₂ standard substance. In addition, when the plating film is comprised of multiple elements such as alloy plating, the thickness of the plating film is evaluated by analyzing a metal element having the highest detection strength except for the main components making up the base material of the element. For example, when a Cu-Sn alloy plating film is formed on the surface of an element mainly comprised of Cu, the thickness of the plating film is measured based on Sn. Further, when forming a Co-Sn alloy plating film on an element mainly comprised of Cu, the thickness of the plating film is measured based on either element having a higher detection intensity.

The shortest distance between the surface of each metal element exposed on the second main surface side of the fastener chain and the first positive electrode in the first electroplating step, and the shortest distance between the surface of each metal element exposed on the first main surface side of the fastener chain and the second positive electrode in the second electroplating step are preferably shorter, respectively, because they can allow efficient plating on each metal element and can allow suppression of plating on unnecessary portions (for example, conductive media). The increased plating efficiency can save maintenance costs, chemicals and electricity for the conductive media. Specifically, the shortest distance between each metal element and the positive electrode is preferably 10 cm or less, and more preferably 8 cm or less, and still more preferably 6 cm or less, and even more preferably 4 cm or less. In this case, it is desirable from the viewpoint of plating efficiency that the first positive electrode and the second positive electrode be disposed so as to extend in parallel to the fastener chain conveying direction.

(3. Plating Device)

Now, embodiments of an electroplating device suitable for carrying out the electroplating method according to the present invention will be described. However, the descriptions of the same components as those described in the embodiments of the electroplating method also apply to those of the embodiments of the electroplating device, and redundant descriptions will be thus omitted in principle.

In one embodiment, the electroplating device according to the present invention includes: <ul id="ul0004" list-style="none" compact="compact"><li>a plating bath capable of accommodating a plating solution;</li><li>a first positive electrode disposed in the plating bath;</li><li>a second positive electrode disposed in the plating bath;</li><li>one or more first insulating container(s) disposed in the plating bath, the first insulating container(s) flowably accommodating a plurality of conductive media in electrical contact with a negative electrode; and</li><li>one or more second insulating container(s) disposed in the plating bath, each of the second insulating container(s) flowably accommodating a plurality of conductive media in electrical contact with a negative electrode.</li></ul>

In the present embodiment, the first insulating container(s) is configured to enable the fastener chain to pass through the first insulating container(s) while mainly bringing a surface of each metal element exposed on the first main surface side of the fastener chain into contact with the conductive media in the first insulating container(s). Further, in the present embodiment, the first positive electrode is disposed in a positional relationship so as to face the surface of each metal element exposed on the second main surface side of the fastener chain during the fastener chain passing through the first insulating container(s). By causing the fastener chain to pass through the first insulating container(s), the surfaces of the element rows exposed on the second main surface side of the fastener chain can be mainly plated.

In the present embodiment, the second insulating container(s) are disposed downstream of the first insulating container(s), and are configured to enable the fastener chain to pass through the second insulating container(s) while mainly bringing a surface of each metal element exposed on the second main surface side of the fastener chain into contact with the conductive media in the second insulating container(s). Further, in the present embodiment, the second positive electrode is disposed in a positional relationship so as to face the surface of each metal element exposed on the first main surface side of the fastener chain during the fastener chain passing through the second insulating container(s). By causing the fastener chain to pass through the second insulating container(s), the surface of the element rows exposed on the first main surface side of the fastener chain can be mainly plated.

In the present embodiment, the device is configured such that a passing distance of the fastener chain from a point where the surface of each metal element exposed on the first main surface side of the fastener chain is initially contacted with the plating solution in the plating bath to a point where the surface of each metal element exposed on the second main surface side of the fastener chain is initially contacted with the conductive media in the second insulating container(s) is within 110 cm. The passing distance within 110 cm can allow an appropriate conveying speed of the fastener chain while enabling the conditions: "power supply to the surface of each metal element exposed on the second main surface side of the fastener chain in the second electroplating step is started within 30 seconds after the surface of each metal element exposed on the first main surface side is initially contacted with the plating solution in the first electroplating step" to be easily achieved. Therefore, the plating device according to the present embodiment is suitable for preventing the displacement plating on the surface of each metal element exposed on the first main surface side.

The passing distance is preferably within 110 cm, and more preferably within 90 cm, and still more preferably within 80 cm, and even more preferably within 60 cm. However, if the passing distance is too short, the plating film does not sufficiently grow on the surface of each metal element exposed on the second main surface side in the first electroplating step. It is also possible to slow down the conveying speed to ensure the growth of the plating film, but this will reduce productivity. Therefore, the passing distance of the fastener chain from the point where the surface of each metal element exposed on the first main surface side of the fastener chain is initially contacted with the plating solution in the plating bath to the point where the surface of each metal element exposed on the second main surface side of the fastener chain is initially contacted with the conductive media in the second insulating container(s) is preferably 30 cm or more, and more preferably 40 cm or more.

The passing distance can be divided into the following three passing distances A-C: <ul id="ul0005" list-style="none" compact="compact"><li>A: a passing distance of the fastener chain from a point where the surface of each metal element exposed on the first main surface side of the fastener chain is initially contacted with the plating solution in the plating bath to an inlet side point where the surface of each metal element exposed on the first main surface side of the fastener chain is initially contacted with the conductive media in the first insulating container(s);</li><li>B: a passing distance from the inlet side point where the surface of each metal element exposed on the first main surface side of the fastener chain is initially contacted with the conductive media in the first insulating container(s) to an outlet side point where the surface of each metal element exposed on the first main surface side of the fastener chain is finally contacted with the conductive media in the first insulating container(s); and</li><li>C: a passing distance from the outlet side point where the surface of each metal element exposed on the first main surface side of the fastener chain is finally contacted with the conductive media in the first insulating container(s) to an inlet side point where the surface of each metal element exposed on the second main surface side of the fastener chain is initially contacted with the conductive media in the second insulating container(s).</li></ul>

To efficiently grow the plating film on the surface of each metal element exposed on the second main surface side in the first electroplating step in a short period of time, it is preferable that the passing distance B which is an electroplating film growing section is lengthened and the distances A and C which are not related to the growth of the electroplating film are shortened as much as possible. From such a viewpoint, A / B ≤ 0.5 is preferable, and A/ B ≤ 0.4 is more preferable, and A/ B ≤ 0.3 is still more preferable. The lower limit of A / B is not particularly set, and it may be, for example, 0.05 ≤ A / B or 0.1 ≤ A / B, in terms of ease of assembly of the device. Similarly, C / B ≤ 1.5 is preferable, C / B ≤ 1.3 is more preferable, and C / B ≤ 1.1 is even more preferable. The lower limit of C / B is not particularly set, and it may be, for example, 0.1 ≤ C / B or 0.5 ≤ C / B, in terms of ease of assembly of the device.

On the other hand, when a passing distance from an inlet side point where the surface of each metal element exposed on the second main surface side of the fastener chain is initially contacted with the conductive media in the second insulating container(s) to an outlet side point where the surface of each metal element exposed on the second surface side of the fastener chain is finally contacted with the conductive media in the second insulating container(s) is defined as D, the passing distance D may be set as needed, because it is not related to the prevention of the displacement plating. However, the passing distance D is preferably equivalent to the passing distance B, because it allows a thin plating film having the equivalent thickness on the surface of the metal element exposed on both of the main surface sides of the fastener chain. Therefore, in one embodiment, the electroplating device according to the present invention can be 0.8 ≤ D / B ≤ 1.2, or 0.9 ≤ D / B ≤ 1.1, or 0.99 ≤ D / B ≤ 1.01.

(4. Specific Structural Example of Plating Device)

Now, a fixed cell type electroplating device which is a specific structural example of the electroplating device according to the present invention will be described. The fixed cell type is advantageous in that only the surface of each metal element exposed on one of the main surfaces can be brought into contact with the conductive media in the insulating container(s). In the fixed cell type plating device, the insulating container(s) is fixed in the plating device and does not involve movement such as rotation. The structure of the insulating container (which can be used for any of the first and second insulating container) according to a structural example of the fixed cell type plating device is schematically shown in <figref idref="f0003 f0004 f0005">FIGS. 3 to 5</figref>. <figref idref="f0003">FIG. 3</figref> is a schematic cross-sectional view of the insulating container of the fixed cell type plating device as viewed from a direction facing the conveying direction of the fastener chain. <figref idref="f0004">FIG. 4</figref> is a schematic cross-sectional view taken along the line A-A' of the insulating container shown in <figref idref="f0003">FIG. 3</figref>. <figref idref="f0005">FIG. 5</figref> is a schematic cross-sectional view taken along the line B-B' when the conductive media and the fastener chain are removed from the insulating container shown in <figref idref="f0003">FIG. 3</figref>.

Referring to <figref idref="f0003">FIGS. 3</figref> and <figref idref="f0004">4</figref>, an insulating container 110 includes: a passage 112 for connecting an inlet 114 to an outlet 115 and for guiding a traveling path of a fastener chain 7; and an accommodating portion 113 for flowably accommodating a plurality of conductive media 11, inside the insulating container 110. The passage 112 includes: the inlet 114 for the fastener chain; the outlet 115 for the fastener chain; one or more opening(s) 117 on a passage surface 112a facing one (first or second) main surface side of the fastener chain 7, the opening(s) 117 enabling access to the conductive media 111; and one or more opening(s) 116 on a passage surface 112b facing the other (second or first) main surface side of the fastener chain 7, the opening(s) 116 enabling fluid communication with the plating solution and current flow. The passage surface 112b may be provided with a guide groove 120 extending along the conveying direction for guiding the conveying direction of the elements 3.

One or more opening(s) 117 enabling access to the conductive media 111 preferably satisfies the relationship: 2D &lt; W₂ &lt; 3D, more preferably 2.1D ≤ W₂ ≤ 2.8D, in which W₂ represents a width in a chain width direction, and D represents a diameter of the conductive medium 111, because power supply is easily stabilized while ensuring a space for movement and rotation of the balls when arranging three balls in the chain width direction so as to partially overlap with one another. Here, the chain width refers to a width of the engaged elements as defined in JIS 3015: 2007. Further, the diameter of the conductive medium is defined as a diameter of a true sphere having the same volume as the conductive medium to be measured.

The fastener chain 7 entering the insulating container 110 from the inlet 114 travels in the direction of the arrow in the passage 112 and exits the outlet 115. While the fastener chain 7 passes through the passage 112, the conductive media 111 held in the accommodating portion 113 can be brought into contact with the surface of each element 3 exposed on one main surface side of the fastener chain 7 through the opening(s) 117. However, there is no opening where the conductive media 111 can access the surface of each element 3 exposed on the other main surface side of the fastener chain 7. Therefore, the conductive media 111 held in the accommodating portion 113 cannot be brought into contact with the surface of each element 3 exposed on the other main surface side of the fastener chain 7.

The conductive media 111 are dragged by the fastener chain 7 traveling in the passage 112 and moved to the front in the conveying direction and are likely to accumulate there. However, excessive accumulation leads to clogging of the conductive media 111 at the front and to strong pressing of the fastener chain 7, so that the conveying resistance of the fastener chain 7 is increased. Therefore, as shown in <figref idref="f0004">FIG. 4</figref>, the outlet 115 is provided at a position higher than the inlet 114 to incline the passage 112 upward, whereby the conductive media 111 contained in the insulating container 110 is returned back in the conveying direction, so that the conveying resistance can be reduced. It is also possible to provide the outlet 115 vertically above the inlet 114 so that the conveying direction of the fastener chain 7 is vertically upward, which makes it easy to control the conveying resistance and provides an advantage of only requiring a small footprint.

Referring to <figref idref="f0005">FIG. 5</figref>, a plate-shaped negative electrode 118 is disposed on a front inner side 113a in the conveying direction among inner sides of the accommodating portion 113. The conductive media 111 can be in electrical contact with the plate-shaped negative electrode 118. Further, while the fastener chain 7 passes through the passage 112, the conductive media 111 can be electrically contacted with the surface of each element 3 exposed on one main surface side of the fastener chain 7. When at least a portion of the conductive media 111 is electrically contacted with both of those conductive media 111 to create an electrical path, power can be supplied to the respective elements 3 while the fastener chain 7 passes through the passage 112.

In a typical embodiment, the fastener chain 7 is electroplated while being immersed in a plating solution. While the fastener chain 7 passes through the passage 112 of the insulating container 110, the plating solution can be contacted with each element 3 by entering the passage 112 through the opening(s) 116. By providing a positive electrode 119 on a side facing the other (second or first) main surface side of the fastener chain 7, cations in the plating solution efficiently reach the other main surface side of the fastener chain, so that the plating film can be rapidly grown on the surface of each element 3 exposed on the main surface side.

It is advantageous for smooth conveying of the fastener chain 7 that the opening(s) 116 formed on the passage surface 112b is provided so as not to catch the fastener chain 7 traveling in the passage 112. From this point of view, each opening 116 is preferably a circular hole, and can be, for example, a circular hole with a diameter of from 1 to 3 mm.

Further, it is preferable to provide the opening(s) 116 formed on the passage surface 112b so that electricity flows with high uniformity throughout the elements 3 of the fastener chain 7 traveling in the passage 112 in order to obtain a highly uniform plating film. From such a point of view, a ratio of an area of the opening(s) 116 to an area including the opening(s) 116 on the passage surface 112b (hereinafter referred to as an opening ratio) is preferably 40% or more, and more preferably 50% or more. However, the opening ratio is preferably 60% or less, for reasons of ensuring strength. Further, as shown in <figref idref="f0005">FIG. 5</figref>, the opening(s) 116 are preferably arranged along the conveying direction of the fastener chain 7 (three rows in <figref idref="f0005">FIG. 5</figref>), and are more preferably arranged in a staggered array from the viewpoint that current flows on the entire exposed surface of the elements 3 to facilitate plating.

Preferably, the conductive media 111 are not contacted with the fastener tape 1 while the fastener chain 7 travels in the passage 112. This is because when the conductive media 111 are contacted with the fastener tape 1, the conveying resistance of the fastener chain is increased. Therefore, the opening(s) 117 are preferably disposed at a position where the conductive media 111 cannot be contacted with the fastener tape. When viewing the insulating container from the direction facing the conveying direction of the fastener chain (see <figref idref="f0003">FIG. 3</figref>), each of gaps C1 and C2 in the chain width direction from both side walls of the opening 117 to both ends of the element 3 is preferably equal to or less than the radius of each conductive medium. However, a narrower distance between both side walls of the opening 117 leads to a decreased contact frequency of the conductive media 111 with the elements 3. Therefore, each of the gaps C1 and C2 is preferably 0 or more, and more preferably larger than 0. The radius of the conductive medium is defined as a radius of a true sphere having the same volume as that of the conductive medium to be measured.

Preferably, the distance between the passage surface 112a and the passage surface 112b is shorter than the diameter of the conductive medium so that the conductive medium does not enter the passage 112. This is because if the conductive medium enters the passage 112, the conveying resistance is significantly increased, which causes the conveying of the fastener chain 7 to be difficult.

<figref idref="f0006 f0007 f0008 f0009 f0010 f0011">FIGS. 6 to 11</figref> show some examples of the overall configuration of the fixed cell type electroplating device. In the embodiment shown in <figref idref="f0006 f0007 f0008 f0009 f0010 f0011">FIGS. 6 to 11</figref>, the fastener chain 7 is conveyed while being guided by a guide roller 214 in the direction of the arrow under tension in the plating bath 201 containing a plating solution 202. The tension is preferably a load of from 0.1N to 0.2N.

(4-1 Vertical Type Electroplating Device)

First, the electroplating device shown in <figref idref="f0006">FIG. 6</figref> will be described. In the electroplating device shown in <figref idref="f0006">FIG. 6</figref>, a plating bath 201 includes: an inlet bath 201a and a main bath 201b. Both of the inlet bath 201a and the main bath 201b can retain the plating solution 202, and both are connected so as to be in communication with the plating solution 202 via a connecting portion 201c at the bottom. In the electroplating device shown in <figref idref="f0006">FIG. 6</figref>, the first insulating container 110a and the second insulating container 110b are immersed in the plating solution in the main bath 201b and arranged in series in the vertical direction. Both of the first insulating container 110a and the second insulating container 110b have vertically extending traveling passages for the fastener chain. The fastener chain 7 enters the plating solution 202 from a plating bath inlet 204 located at the top of the inlet bath 201a, and then travels vertically downward to the bottom of the inlet bath 201a. After reaching the bottom, the fastener chain 7 enters the main bath 201b through the connecting portion 201c. The fastener chain 7 passes through the first insulating container 110a and the second insulating container 110b in this order in the vertical upward direction, then exits the plating solution 202, and then exits a plating bath outlet 205 disposed at a top side of the main bath 201b.

A liquid level of the inlet bath 201a lower than a liquid level of the main bath 201b can allow a shorter passing distance of the fastener chain 7 from a point P where the surface of each metal element exposed on the first main surface side of the fastener chain 7 is initially contacted with the plating solution in the plating bath to the inlet 114a of the first insulating container 110a. For example, the liquid level of the plating solution in the inlet bath 201a is preferably 0.6 times or less, more preferably 0.5 times or less, even more preferably 0.4 times or less as high as the liquid level of the plating solution in the main bath 201b. However, if the liquid level of the plating solution in the inlet bath 201a is excessively lowered, a difference of elevation between the liquid levels will be large, and an amount of a liquid from the point P is increased, so that the feeding from the pump has to be increased. Therefore, for example, the liquid level of the plating solution in the inlet bath 201a is preferably 0.1 times or more, more preferably 0.2 times or more, even more preferably 0.3 times or more as high as the liquid level of the plating solution in the main bath 201b.

The plating solution 202 in the inlet bath 201a overflows from the plating bath inlet 204 due to the difference in liquid level. The plating solution 202 which has flowed out due to the overflow is collected in a storage tank 203, and then fed to the main bath 201b through a feed pipe 212 by means of a circulation pump 208. A heater may be installed in the storage tank 203 to heat the plating solution therein. The plating bath inlet 204 may be provided with a flow restricting member 218 for suppressing the flow of the plating solution 202 that overflows. The flow restricting member 218 can also be provided in the connecting portion 201c.

In the electroplating device shown in <figref idref="f0006">FIG. 6</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one of the main surface sides of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the fastener chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b.

In the electroplating device shown in <figref idref="f0006">FIG. 6</figref>, the fastener chain 17 exits the first insulating container 110a, and then enters the second insulating container 110b without changing its route. In other words, since the fastener chain 7 passes through the first insulating container 110a and the second insulating container 110b while going straight, the distance between the outlet 115a for the first insulating container 110a and the inlet 114b for the second insulating container 110b can be shortened.

The electroplating device shown in <figref idref="f0006">FIG. 6</figref> is provided with an insulating partition plate 121 for electrical disconnection to prevent mutual influence between the first insulating container 110a and the second insulating container 110b. The material of the partition plate 121 is not particularly limited as long as it is an insulator, and the partition plate 121 may be made of a resin such as a vinyl chloride resin, for example.

Next, the electroplating device shown in <figref idref="f0007">FIG. 7</figref> will be described. In the electroplating device shown in <figref idref="f0007">FIG. 7</figref>, the first insulating container 110a and the second insulating container 110b are also arranged in series in the vertical direction while being immersed in the plating solution in the plating bath 201. However, in the electroplating device shown in <figref idref="f0007">FIG. 7</figref>, there is no inlet bath as shown in <figref idref="f0006">FIG. 6</figref>. In the electroplating device shown in <figref idref="f0007">FIG. 7</figref>, the fastener chain 7 enters the plating solution 202 from the plating bath inlet 204 located at the bottom of the plating bath 201 while being conveyed vertically upward. The fastener chain 7 then passes through the first insulating container 110a and the second insulating container 110b in this order vertically upward without changing the route, then exits the plating solution 202 and then exits the plating bath outlet 205 disposed at a top side of the plating bath 201.

Thus, in the electroplating device shown in <figref idref="f0007">FIG. 7</figref>, the fastener chain 7 enters the plating solution 202 from the plating bath inlet 204, and travels straight ahead without changing the route until the fastener chain reaches the inlet 114a for the first insulating container 110a, thereby allowing a shorter passing distance of the faster chain from the point P where the surface of each metal element exposed on the first main surface side of the fastener chain 7 is initially contacted with the plating solution in the plating bath 201 to the inlet 114a for the first insulating container. Moreover, in the electroplating device shown in <figref idref="f0007">FIG. 7</figref>, the fastener chain 7 exits the first insulating container 110a, and then enters the second insulating container 110b without changing its route. In other words, since the fastener chain 7 passes through the first insulating container 110a and the second insulating container 110b while going straight, the distance between the outlet 115a for the first insulating container 110a and the inlet 114b for the second insulating container 110b can be shortened.

In the electroplating device shown in <figref idref="f0007">FIG. 7</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one of the main surface sides of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b. According to this embodiment, double-sided plating can be performed in one plating bath, so that the installation space can be reduced.

The electroplating device shown in <figref idref="f0007">FIG. 7</figref> is provided with an insulating partition plate 121 for electrical disconnection to prevent mutual influence between the first insulating container 110a and the second insulating container 110b. The material of the partition plate 121 is not particularly limited as long as it is an insulator, and the partition plate 121 may be made of a resin such as a vinyl chloride resin, for example.

In the electroplating device shown in <figref idref="f0007">FIG. 7</figref>, the plating bath 201 has a discharge port 209 at an upper portion such that the plating solution 202 in the plating bath 201 can overflow. The plating solution 202 which has flowed out due to the overflow is collected in the storage tank 203 and then fed to the plating bath 201 through the feed pipe 212 by means of the circulation pump 208. Further, the plating solution 202 in the plating bath 201 leaks out from the plating bath inlet 204. The leaking plating solution 202 is collected in the storage tank 203 and then fed to the plating bath 201 through the feed pipe 212 by means of the circulation pump 208. A heater may be disposed in the storage tank 203 to heat the plating solution therein. The plating bath inlet 204 may be provided with a flow restricting member 218 to suppress the flow of the leaking plating solution 202.

(4-2 Horizontal Type Electroplating Device)

Next, the electroplating device shown in <figref idref="f0008">FIG. 8</figref> will be described. In the embodiment shown in <figref idref="f0008">FIG. 8</figref>, the first insulating container 110a and the second insulating container 110b are immersed in the plating solution in the plating bath 201. Both of the first insulating container 110a and the second insulating container 110b have horizontally extending traveling passages for the fastener chain. The first insulating container 110a and the second insulating container 110b are arranged adjacent to each other so that the traveling directions of the fastener chains are parallel and opposite to each other in the plan view.

The fastener chain 7 enters the plating solution 202 from up above the plating solution surface, and then passes through the first insulating container 110a while advancing straight in the horizontal direction. After leaving the first insulating container 110a, the fastener chain 7 is guided by a inverting guide roller 216 having an axis extending in the horizontal direction, and is inverted while moving in the axial direction of the inverting guide roller 216. After being inverted, the fastener chain 7 in which the up and down direction of the main surface has been inverted passes through the second insulating container 110b while going straight in the horizontal direction, and exits the plating solution 202.

In the electroplating device shown in <figref idref="f0008">FIG. 8</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one of the main surface sides of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b. According to this embodiment, double-sided plating can be performed in one plating bath, so that the installation space can be reduced.

In the electroplating device shown in <figref idref="f0008">FIG. 8</figref>, each of the first insulating container 110a and the second insulating container 110b has a traveling passage for the fastener chain, which extends in the horizontal direction, so that a depth of the plating solution can be reduced. For example, the depth of the plating solution can be 30 cm or less, further 25 cm or less, for example from 16 to 21 cm. Therefore, even if the fastener chain 7 is fed from up above the plating solution surface in the plating bath 201, the passing distance of the fastener chain 7 from the point P where the surface of each metal element exposed on the first main surface side of the fastener chain 7 is initially contacted with the plating solution in the plating bath 201 to the inlet 114a for the first insulating container can be sufficiently shortened.

Further, in the electroplating device shown in <figref idref="f0008">FIG. 8</figref>, top sides of the first insulating container 110a and the second insulating container 110b do not overlap with each other, so that the conductive media 111 contained inside them can be easily accessed from the top side to facilitate loading and unloading of the conductive media 111. In this regard, the present embodiment has improved maintainability. Furthermore, in the electroplating device shown in <figref idref="f0008">FIG. 8</figref>, the plating solution in the plating bath 201 does not decrease due to the overflow, so that a pump for returning the plating solution back to the plating bath and a storage tank for the plating solution are not required. Therefore, a cost for the plating device can be reduced.

(4-3 Inclined Type Electroplating Device)

Next, the electroplating device shown in <figref idref="f0009">FIG. 9</figref> will be described. In the electroplating device shown in <figref idref="f0009">FIG. 9</figref>, the first insulating container 110a and the second insulating container 110b are immersed in the plating solution in the plating bath 201. Both of the first insulating container 110a and the second insulating container 110b have traveling passages for the fastener chain 7 inclined upward. The first insulating container 110a and the second insulating container 110b are arranged adjacent to each other so that the traveling directions of the fastener chains are parallel to each other and opposite to each other in the plan view.

The fastener chain 7 enters the plating solution 202 from up above the plating solution surface, and then passes through the first insulating container 110a while advancing straight upward. The fastener chain 7 that has exited the first insulating container 110a is then guided by a inverting guide roller 216 having an axis extending in the horizontal direction, and is inverted while moving in the axial direction of the inverting guide roller 216. After being inverted, the fastener chain 7 in which the up and down direction of the main surface has been inverted passes through the second insulating container 110b while advancing straight, and exits the plating solution 202. Since a depth of the plating solution 202 can be reduced if inclination angles of the first insulating container 110a and the second insulating container 110b are small, the passing distance of the fastener chain 7 from the point P where the surface of each metal element exposed on the first main surface side of the fastener chain 7 is initially contacted with the plating solution in the plating bath 201 to the inlet 114a for the first insulating container can be sufficiently shortened.

In the electroplating device shown in <figref idref="f0009">FIG. 9</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one of the main surface sides of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b. According to this embodiment, double-sided plating can be performed in one plating bath, so that the installation space can be reduced. Further, in the electroplating device shown in <figref idref="f0009">FIG. 9</figref>, the first insulating container 110a and the second insulating container 110b are inclined upward, so that the conveying resistance of the fastener chain 7 due to the conductive media 111 inside them can be reduced.

Further, in the electroplating device shown in <figref idref="f0009">FIG. 9</figref>, top sides of the first insulating container 110a and the second insulating container 110b do not overlap with each other, so that the conductive media 111 contained inside them can be easily accessed from the top side to facilitate loading and unloading of the conductive media 111. In this regard, the present embodiment has improved maintainability.

Next, the electroplating device shown in <figref idref="f0010">FIG. 10</figref> will be described. In the electroplating device shown in <figref idref="f0010">FIG. 10</figref>, the first insulating container 110a and the second insulating container 110b are immersed in the plating solution 202 in the plating bath 201. Both of the first insulating container 110a and the second insulating container 110b have traveling passages for the fastener chain 7 inclined upward. The first insulating container 110a and the second insulating container 110b are arranged so as to overlap with each other vertically such that the traveling directions of the fastener chains are parallel to each other and opposite to each other in the plan view.

The fastener chain 7 enters the plating solution 202 from the plating bath inlet 204 provided at the lateral side of the plating bath 201, and then passes through the first insulating container 110a while going straight in an obliquely upward direction. The fastener chain 7 that has exited the first insulating container 110a is then guided by a inverting guide roller 216 having an axis extending in a horizontal direction, and is inverted without being moved in the axial direction of the inverting guide roller 216. After being inverted, the fastener chain 7 in which the up and down direction of the main surface has been inverted passes through the second insulating container 110b disposed on an upper side of the first insulating container 110a while going straight in the obliquely upward direction, and exits the plating solution 202.

In the electroplating device shown in <figref idref="f0010">FIG. 10</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one of the main surface sides of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b. According to this embodiment, double-sided plating can be performed in one plating bath, so that the installation space can be reduced.

In the electroplating device shown in <figref idref="f0010">FIG. 10</figref>, the plating solution 202 in the plating bath 201 leaks out from the plating bath inlet 204. The leaking plating solution 202 is collected in the storage tank 203 and then fed to the plating bath 201 through the feed pipe 212 by means of the circulation pump 208. A heater may be disposed in the storage tank 203 to heat the plating solution therein.

Further, in the electroplating device shown in <figref idref="f0010">FIG. 10</figref>, the first insulating container 110a and the second insulating container 110b are arranged in the vertical direction, so that the fastener chain 7 is not moved in the axial direction when it is inverted by the guide roller 216. Therefore, the inverting operation is smoothed, thereby providing an advantage that it is possible to reduce a risk that the fastener chain is caught by the inverting guide roller 216 to stop the conveying.

The electroplating device shown in <figref idref="f0010">FIG. 10</figref> is provided with an insulating partition plate 121 for electrical disconnection to prevent mutual influence between the first insulating container 110a and the second insulating container 110b. The material of the partition plate 121 is not particularly limited as long as it is an insulator, and the partition plate 121 may be made of a resin such as vinyl chloride resin, for example.

Next, the electroplating device shown in <figref idref="f0011">FIG. 11</figref> will be described. In the electroplating device shown in <figref idref="f0011">FIG. 11</figref>, the first insulating container 110a and the second insulating container 110b are immersed in the plating solution in the plating bath 201. Both of the first insulating container 110a and the second insulating container 110b have traveling passages for the fastener chain 7 inclined upward. The first insulating container 110a and the second insulating container 110b are disposed back and front so that the traveling direction of the fastener chain is on a straight line in the plan view.

The fastener chain 7 enters the plating solution 202 from up above the plating solution surface, and then passes through the first insulating container 110a while advancing straight upward. The fastener chain 7 that has exited the first insulating container 110a then enters the second insulating container 110b after the front and back are inverted. The fastener chain 7 in which the front and back have been inverted passes the second insulating container 110b while advancing straight, and exits the plating solution 202. A method for inverting the fastener chain 7 is not particularly limited. However, gradual inverting for a longer distance can weaken a force to resist the inverting. Therefore, it is desirable that a distance of 20 cm or more is ensured from the outlet of the first insulating container 110a to the inlet of the second insulating container 110b.

In the electroplating device shown in <figref idref="f0011">FIG. 11</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one of the main surface sides of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b. According to this embodiment, double-sided plating can be performed in one plating bath, so that the installation space can be reduced. Further, in the electroplating device shown in <figref idref="f0011">FIG. 11</figref>, the first insulating container 110a and the second insulating container 110b are inclined upward, so that the conveying resistance of the fastener chain 7 due to the conductive media 111 inside them can be reduced.

Further, in the electroplating device shown in <figref idref="f0011">FIG. 11</figref>, top sides of the first insulating container 110a and the second insulating container 110b do not overlap with each other, so that the conductive media 111 contained inside them can be easily accessed from the top side to facilitate loading and unloading of the conductive media 111. In this regard, the present embodiment has improved maintainability.

EXAMPLES

Hereinafter, Examples of the present invention are illustrated, but they are provided for better understanding of the present invention and its advantages, and are not intended to limit the present invention.

(Comparative Example 1)

The electroplating device shown in <figref idref="f0012">FIG. 12</figref> was constructed, and electroplating was continuously performed on a fastener chain being conveyed. In the electroplating device, an insulating container 110 containing a large number of conductive media 111 is disposed in a plating bath 201 containing a plating solution 202. A negative electrode 118 is provided at a center of the inside of the insulating container 110, and the conductive media 111 are in electrical contact with the negative electrode. The insulating container 110 has positive electrodes 119 on front and rear inner sides with respect to the traveling direction of the fastener chain 7. In this example, while the fastener chain 7 passes through the plating solution 202, the conductive media randomly contact the elements exposed on both main surface sides of the fastener chain 7, thereby forming the plating film on the surfaces of the elements.

The plating conditions were as follows: <ul id="ul0006" list-style="dash" compact="compact"><li>Fastener chain specification: model 5 RG chain (a chain width: 5.75 mm; element material: red brass) from YKK Corporation:</li><li>Plating solution: 5 L; composition: a plating solution for Sn-Co alloy plating;</li><li>Conductive media: 2700 stainless steel balls; diameter 4.5 mm; and</li><li>Current density: 5 A/dm².</li></ul> The current density was a value obtained by dividing a current value (A) of a rectifier by a sum (dm²) of the total surface area (both sides) of the elements in a glass container and surface areas of the stainless steel balls. The reason why the surface areas of the stainless steel balls are taken into consideration is that the plating also adheres to the stainless steel balls. <ul id="ul0007" list-style="dash" compact="compact"><li>Retention time in plating solution: 7.2 seconds;</li><li>Conveying speed: 2.5 m/min; and</li><li>Insulating container: glass beaker.</li></ul>

(Example 1)

Insulating containers each having the structure shown in <figref idref="f0003 f0004 f0005">FIGS. 3 to 5</figref> were produced according to the following specifications: <ul id="ul0008" list-style="dash" compact="compact"><li>Conductive Media: 450 iron balls having a copper pyrophosphate plating film with a thickness of about 3 µm on their surfaces, and having a diameter of 4.5 mm; number of laminated layers = 6;</li><li>Insulating Container: made of an acrylic resin;</li><li>Inclination Angle: 9°;</li><li>Openings 116: 54% opening ratio; circular holes having a diameter of 2 mm, arranged in a staggered pattern;</li><li>Gaps C1, C2: 2 mm;</li><li>Width W₂: 10 mm.</li></ul>

The electroplating device shown in <figref idref="f0009">FIG. 9</figref> was constructed using the above insulating containers, and electroplating was continuously performed on the fastener chain being conveyed. <ul id="ul0009" list-style="dash" compact="compact"><li>Fastener Chain Specification: model 5 RG chain (chain width: 5.75 mm, element material: red brass) from YKK Corporation;</li><li>Plating Solution: 40 L, composition: non-cyan copper strike plating solution;</li><li>Voltage: 5V;</li><li>Plating Time: 9 seconds.</li></ul> The plating time is a time required for each element to pass through one insulating container (plating time per side). <ul id="ul0010" list-style="dash" compact="compact"><li>Time from the first contact of the surface of each metal element exposed on the first main surface side in the first electroplating step with the plating solution to the start of power supply to the surface of each metal element exposed on the second main surface side of the fastener chain in the second electroplating step (hereinafter referred to as "stand-by time to second electroplating"): 30 seconds;</li><li>Conveying Speed: 2 m/min;</li><li>The shortest distance between each element and the positive electrode: 3 cm;</li><li>Passing distance A (as defined above): 10 cm;</li><li>Passing distance B (as defined above): 40 cm; and</li><li>Passing distance C (as described above): 50 cm; and</li><li>Passing distance D (as defined above): 40 cm.</li></ul>

(Examples 2 to 5 and Comparative Examples 2 to 3)

Electroplating was continuously performed on the fastener chain being conveyed by the same method as that of Example 1, with the exception that the plating time was adjusted by changing the structure of the electroplating device such that the passing distances A to C satisfied the conditions shown in Table 1. <tables id="tabl0001" num="0001"><table frame="all"><title>[Table 1-1]</title><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="28mm" /><colspec colnum="2" colname="col2" colwidth="32mm" /><colspec colnum="3" colname="col3" colwidth="32mm" /><colspec colnum="4" colname="col4" colwidth="32mm" /><colspec colnum="5" colname="col5" colwidth="16mm" /><colspec colnum="6" colname="col6" colwidth="14mm" /><colspec colnum="7" colname="col7" colwidth="14mm" /><thead><row><entry valign="middle" /><entry align="center" valign="middle">Passing Distance A (cm)</entry><entry align="center" valign="middle">Passing Distance B (cm)</entry><entry align="center" valign="middle">Passing Distance C (cm)</entry><entry align="center" valign="middle">A+B+C</entry><entry align="center" valign="middle">A/B</entry><entry align="center" valign="middle">C/B</entry></row></thead><tbody><row><entry valign="middle">Comparative Example 2</entry><entry align="center" valign="middle">20</entry><entry align="center" valign="middle">60</entry><entry align="center" valign="middle">37</entry><entry align="center" valign="middle">117</entry><entry align="center" valign="middle">0.333</entry><entry align="center" valign="middle">0.617</entry></row><row><entry valign="middle">Comparative Example 3</entry><entry align="center" valign="middle">20</entry><entry align="center" valign="middle">60</entry><entry align="center" valign="middle">53</entry><entry align="center" valign="middle">133</entry><entry align="center" valign="middle">0.333</entry><entry align="center" valign="middle">0.883</entry></row><row><entry valign="middle">Example 1</entry><entry align="center" valign="middle">10</entry><entry align="center" valign="middle">40</entry><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">0.250</entry><entry align="center" valign="middle">1.250</entry></row><row><entry valign="middle">Example 2</entry><entry align="center" valign="middle">10</entry><entry align="center" valign="middle">40</entry><entry align="center" valign="middle">33</entry><entry align="center" valign="middle">83</entry><entry align="center" valign="middle">0.250</entry><entry align="center" valign="middle">0.825</entry></row><row><entry valign="middle">Example 3</entry><entry align="center" valign="middle">5</entry><entry align="center" valign="middle">30</entry><entry align="center" valign="middle">32</entry><entry align="center" valign="middle">67</entry><entry align="center" valign="middle">0.167</entry><entry align="center" valign="middle">1.067</entry></row><row><entry valign="middle">Example 4</entry><entry align="center" valign="middle">5</entry><entry align="center" valign="middle">30</entry><entry align="center" valign="middle">15</entry><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">0.167</entry><entry align="center" valign="middle">0.500</entry></row><row><entry valign="middle">Example 5</entry><entry align="center" valign="middle">5</entry><entry align="center" valign="middle">20</entry><entry align="center" valign="middle">8</entry><entry align="center" valign="middle">33</entry><entry align="center" valign="middle">0.250</entry><entry align="center" valign="middle">0.400</entry></row></tbody></tgroup></table></tables><tables id="tabl0002" num="0002"><table frame="all"><title>[Table 1-2]</title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="38mm" /><colspec colnum="2" colname="col2" colwidth="59mm" /><colspec colnum="3" colname="col3" colwidth="41mm" /><thead><row><entry valign="middle" /><entry align="center" valign="middle">Stand-by Time to Second Electroplating</entry><entry align="center" valign="middle">Passing Distance D (cm)</entry></row></thead><tbody><row><entry valign="middle">Comparative Example 2</entry><entry align="center" valign="middle">35 seconds</entry><entry align="center" valign="middle">60</entry></row><row><entry valign="middle">Comparative Example 3</entry><entry align="center" valign="middle">40 seconds</entry><entry align="center" valign="middle">60</entry></row><row><entry valign="middle">Example 1</entry><entry align="center" valign="middle">30 seconds</entry><entry align="center" valign="middle">40</entry></row><row><entry valign="middle">Example 2</entry><entry align="center" valign="middle">25 seconds</entry><entry align="center" valign="middle">40</entry></row><row><entry valign="middle">Example 3</entry><entry align="center" valign="middle">20 seconds</entry><entry align="center" valign="middle">30</entry></row><row><entry valign="middle">Example 4</entry><entry align="center" valign="middle">15 seconds</entry><entry align="center" valign="middle">30</entry></row><row><entry valign="middle">Example 5</entry><entry align="center" valign="middle">10 seconds</entry><entry align="center" valign="middle">20</entry></row></tbody></tgroup></table></tables>

(Plating Uniformity)

For the above Examples and Comparative Example, evaluation results obtained by visually observing the resulting plating film of each element of the fastener chain are shown below: Evaluation was performed according to the following procedure. Each element is subjected to investigation whether or not plating is attached to both of the front and back sides. The evaluation of whether or not plating is attached to each element is carried out based on whether or not the element surface is entirely changed to copper color by visual inspection. It is determined that the plating is attached to the element only when the plating is attached to both of the front and back surfaces of the element. The investigation is performed for 200 elements which are adjacent to each other, and a ratio (%) of the number of elements to which plating adheres on both the front and back surfaces is calculated. The results are shown in Table 2. The results are shown as average values when the same plating tests were performed multiple times. <tables id="tabl0003" num="0003"><table frame="all"><title>[Table 2]</title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="38mm" /><colspec colnum="2" colname="col2" colwidth="47mm" /><thead><row><entry valign="middle" /><entry align="center" valign="middle">Plating Uniformity Evaluation</entry></row></thead><tbody><row><entry valign="middle">Comparative Example 1</entry><entry align="center" valign="middle">90%</entry></row><row><entry valign="middle">Comparative Example 2</entry><entry align="center" valign="middle">90 % or more</entry></row><row><entry valign="middle">Comparative Example 3</entry><entry align="center" valign="middle">90 % or more</entry></row><row><entry valign="middle">Example 1</entry><entry align="center" valign="middle">99 % or more</entry></row><row><entry valign="middle">Example 2</entry><entry align="center" valign="middle">99 % or more</entry></row><row><entry valign="middle">Example 3</entry><entry align="center" valign="middle">99 % or more</entry></row><row><entry valign="middle">Example 4</entry><entry align="center" valign="middle">99 % or more</entry></row><row><entry valign="middle">Example 5</entry><entry align="center" valign="middle">99 % or more</entry></row></tbody></tgroup></table></tables>

(Thickness of Plating film)

For the above Comparative Examples 2 to 3 and Examples 1 to 6, a thickness of plating film at the element center Q of each element exposed on both of the main surface sides of the fastener chain was measured for arbitrary 20 elements by the method as described above, indicating that plating film having a thickness of about 0.1 µm was formed at the element center Q of the metal elements exposed on both of the main surface sides.

(Plating Adhesiveness)

For the above Examples 1 to 5 and Comparative Examples 2 to 3, adhesiveness of plating film to the surface of the elements exposed on both of the main surface sides of the fastener chain was evaluated. The evaluation method was as follows: two longitudinal scratches and two transverse scratches (#) were put on the plated surface by means of a cutter until the scratches reached the base material. A cellophane tape was attached onto the plated surface and pressed with a finger, and the cellophane tape was then peeled off, and the presence or absence of a peeled plating film at the # cut portions was visually observed. Table 3 shows a percentage of the number of elements absent of peeled plating film out of 100 elements. <tables id="tabl0004" num="0004"><table frame="all"><title>[Table 3]</title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="28mm" /><colspec colnum="2" colname="col2" colwidth="69mm" /><colspec colnum="3" colname="col3" colwidth="69mm" /><thead><row><entry valign="middle" /><entry namest="col2" nameend="col3" align="center" valign="middle">Plating Adhesiveness</entry></row><row><entry valign="middle" /><entry align="center" valign="middle">Plating Film on First Main Surface Side (Plating Film Formed by Second Electroplating)</entry><entry align="center" valign="middle">Plating Film on Second Main Surface Side (Plating Film Formed by First Electroplating)</entry></row></thead><tbody><row><entry valign="middle">Comparative Example 2</entry><entry align="center" valign="middle">90%</entry><entry align="center" valign="middle">90%</entry></row><row><entry valign="middle">Comparative Example 3</entry><entry align="center" valign="middle">90%</entry><entry align="center" valign="middle">90%</entry></row><row><entry valign="middle">Example 1</entry><entry align="center" valign="middle">99 % or more</entry><entry align="center" valign="middle">99 % or more</entry></row><row><entry valign="middle">Example 2</entry><entry align="center" valign="middle">99 % or more</entry><entry align="center" valign="middle">99 % or more</entry></row><row><entry valign="middle">Example 3</entry><entry align="center" valign="middle">99 % or more</entry><entry align="center" valign="middle">99 % or more</entry></row><row><entry valign="middle">Example 4</entry><entry align="center" valign="middle">99 % or more</entry><entry align="center" valign="middle">99 % or more</entry></row><row><entry valign="middle">Example 5</entry><entry align="center" valign="middle">99 % or more</entry><entry align="center" valign="middle">99 % or more</entry></row></tbody></tgroup></table></tables>

<Discussion>

Each of Examples 1 to 5 could uniformly form plating films having high adhesiveness to the surfaces of the elements exposed on both of the main surface sides of the fastener chain. In contrast, Comparative Example 1 could not provide plating film having high uniformity. Comparative Examples 2 and 3 had the high uniformity of the plating film, but could not provide a plating film having high adhesiveness as compared with Examples 1 to 5. This would be because, in Comparative Examples 2 and 3, the stand-by time to the second electroplating was longer, and the displacement plating with poor adhesion was significantly generated on the surface of each metal element exposed on the first main surface side. It should be noted that the iron balls for power supply was spaced apart from the positive electrode and surrounded by a resin container, so that almost no plating film adhered to the iron balls.

(Example 6)

Electroplating was continuously performed on the fastener chain being conveyed under the same conditions as those of Example 1 with the exception that the conditions for electroplating were changed as follows: <ul id="ul0011" list-style="dash"><li>Composition: non-cyan gold plating solution; and</li><li>Voltage: 3V.</li></ul>

(Plating Uniformity)

Whether or not the resulting plating films adhered to both of the front and back surfaces of each element was investigated by visually observing the plating films of the elements of the fastener chain by visual observation using the same method as that of Example 1. However, in this example, the presence or absence of the plating adhesion was evaluated based on whether or not the element surface was entirely changed to gold color. As a result, 99% or more of the elements were plated.

(Thickness of Plating film)

In Example 6, thickness of plating film at the element center Q of each element exposed on both of the main surface sides of the fastener chain was measured for arbitrary five elements by the method as described above, indicating a plating film having a thickness of about 0.05 µm was formed at the element center Q of the element exposed on both of the main surface sides.

(Plating Adhesiveness)

Adhesiveness of plating film to the surface of the elements exposed on both of the main surface sides of the fastener chain in Example 6 was evaluated in the same method as that of Example 1. As a result, the adhesiveness was confirmed for 99% or more of elements.

DESCRIPTION OF REFERENCE NUMERALS

<ul id="ul0012" list-style="none" compact="compact"><li>1 fastener tape</li><li>2 core potion</li><li>3 element</li><li>4 upper stopper</li><li>5 lower stopper</li><li>6 slider</li><li>7 fastener chain</li><li>9 head portion</li><li>10 leg portion</li><li>110 insulating container</li><li>110a first insulating container</li><li>110b second insulating container</li><li>111 conductive medium</li><li>112 passage</li><li>112a passage surface facing the first main surface side of fastener chain</li><li>112b passage surface facing the second main surface of the fastener chain</li><li>113 accommodating portion</li><li>113a front inner side in the conveying direction of accommodating portion</li><li>113b inner side parallel to the conveying direction of accommodating portion</li><li>114a inlet for first insulating container</li><li>114b inlet for second insulating container</li><li>115a outlet for first insulating container</li><li>115b outlet for second insulating container</li><li>116 opening</li><li>117 opening</li><li>118 negative electrode</li><li>119 (119a, 119b) positive electrode</li><li>120 guide groove</li><li>121 partition plate</li><li>201 plating bath</li><li>202 plating solution</li><li>203 storage tank</li><li>204 plating bath inlet</li><li>205 plating bath outlet</li><li>208 circulating pump</li><li>209 discharge port</li><li>212 feed pipe</li><li>214 guide roller</li><li>216 inverting guide roller</li><li>218 flow restricting member</li></ul>